Category: #FOAMpeds

Case: 5yo M comes into the ED with nausea, confusion, and headache. On exam, he is sleepy but noticeable uncomfortable. He has moist mucous membranes, pupils are reactive and he has no noticeable edema. Suddenly, he begins to have a generalized tonic-clonic seizures. Amid the chaos and his mother’s crying you check a BMP and lo and behold his Na comes back as 125!

What is the pathophysiology of hyponatremia?

When there is an acute drop in sodium in the blood, water is pulled into the intracellular fluid so cells, especially brain cells, begin to swell. This causes meningeal irritation and the manifested symptoms of nausea, confusion, headache, vomiting and eventually, seizures.

Effects of Hyponatremia on the Brain and Adaptive Responses

Image from: Adrogue HJ et al, 2000

What is the workup of hyponatremia?

Choice of diagnostic algorithms:

Classic algorithm begins with an evaluation of patient’s fluid status.

This is notoriously difficult to do accurately and clinicians have been shown to be very inaccurate in their assessment with sensitivities ranging from 0.5-0.8 and specificities 0.3-0.5 (Chung HM et al, 1987)

Alternative algorithm: (Milionis HJ et al, 2002).

Application of Alternative Algorithm

(Adapted from Milionis HJ et al, 2002)

Step 1: Verify this is an accurate level and is not spuriously low

Step 2: Obtain serum osmolality: (normal 275-290)

Low serum osmolality: True hyponatremia

Normal serum osmolality: Results from either large volumes of isotonic fluid lacking sodium (most common = mannitol), or in cases of hyperparaproteinemia or hyperlipidemia/triglyceridemia, that latter cases being referred to as “pseudohyponatremia” (see below for illustration). This is only seen in labs that use flame photometry; newer methods using ion-specific electrode have nearly eliminated this entity (Androgue HJ et al, 2000).

We are so excited to launch the OPENPediatrics Critical Care Curriculum! The OPENPediatrics platform will have two purposes.

The Guided Learning Pathway is designed to teach you the bread and butter of critical care.

The second component is a Group page that will have additional educational material outside the OPENPediatrics curriculum. We will invite each resident to the group page. We encourage residents to send any interesting data or learning material to us. We will review the material with the critical care team and then uploaded onto the group page.